A photoelectric conversion device includes a photoelectric conversion region having a plurality of photoelectric conversion elements and a first MOS transistor configured to read a signal in response to an electric charge of each photoelectric conversion element; and a peripheral circuit region having a second MOS transistor configured to drive the first MOS transistor and/or amplify the signal read from the photoelectric conversion region, the photoelectric conversion region and the peripheral circuit region being located on the same semiconductor substrate, wherein an impurity concentration in a drain of the first MOS transistor is lower than an impurity concentration in a drain of the second MOS transistor.